Various techniques for separating cells are known, e.g., the one for separating cells using mainly, as an index, physical properties of cells, such as, morphology, size, specific gravity, or biochemical properties of cells, etc. Among them, FACS (fluorescence activated cell sorting) and MACS (magnetic activated cell sorting) are the methods that are recently used. These methods distinguish only target cells in cell samples, using a fluorescence-labeled antibody or a magnetically-labeled antibody. In FACS, cell samples in a liquid flow are irradiated with a laser beam, and a fluorescence emitted by each cell in the cell samples is measured, thereby target cells are distinguished, and only the target cells are sorted. These methods are the ones for targeting an antigen on surfaces of a cell, and are not the ones for discriminating and separating target cells using, as a marker, an intracellular substance, such as protein, etc., produced within each target cell. In FACS, it is possible to use an intracellular protein as a marker by the method for producing a fusion protein with a fluorescence protein through gene recombination, however, genetically-modified cells cannot be used when it is intended to separate natural cells for use in transplant treatment. Further, in FACS, a highly precise control mechanism is needed for causing fluorescence measurement results to closely work with sorting, inevitably making it extremely expensive, and moreover, there has been a problem that a fluorescence-labeled antibody must be used.
On the other hand, the inventor of the present application has developed a cell-manipulating apparatus that inserts a needle-shaped body with a nano-level diameter (hereinafter, sometimes referred to as a nanoneedle), on which a gene or a gene expression-related substance has been immobilized, into a cell, and that enables observation of effects of the immobilized substance on the cell in real time, while detecting positions of the needle-shaped body within the cell based on a force response the cell exerts against the needle-shaped body (see Japanese Patent Registration No. 4051440). The inventor of the present application has further developed the technique of Japanese Patent Registration No. 4051440, and discovered that it is possible to detect a target protein in a cell by inserting a nanoneedle with a diameter of 200 nm, which has been modified by an antibody against the target protein, into the cell, and measuring a force response exerted against the nanoneedle when the nanoneedle is withdrawn from the cell (see Japanese Unexamined Patent Application Publication No. 2006-246731).
However, at the time when the above-described results were obtained, it was not conceived to apply these technologies to separation of target cells.
Patent Document 1: Japanese Patent Registration No. 4051440
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2006-246731